Journal of Coatings Technology and Research最新文献

Emulsion polymerization acrylic latex polymers (in short latex polymers), crucial ingredients of waterborne paints, provide continuous film formation during the drying stage and act as one of the major factors that determine the performance of paints. Modification of latex polymers is an ongoing process to improve paint performance and it can be accomplished by various methods. In this study, styrene and n-butyl acrylate latex polymers are modified by three functional monomers (methacrylamidoethyl ethylene urea (MAEEU), dimethylaminoethyl methacrylate (DMAEMA), and glycidyl methacrylate (GMA)) alone or combined in different amounts in latex polymer formulations. Impacts of these functional monomers both on latex polymers, and paints made from these latex polymers are investigated. The characterization of the latex polymers are analyzed by differential scanning calorimetry (DSC), minimum film forming temperature (MFFT), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). Scrub resistance, whiteness, hiding power, glossiness, hardness, contact angle, adhesion on annealed glass and hot-dip galvanized steel surfaces, and color retention properties of the paints are examined. The results are compared with a nonfunctional reference and a commercial styrene-acrylic-based latex polymer, separately. The outcomes confirm that alone and the combinations of these monomers in styrene-acrylic-based latex polymers improve the paint by enhancing scrub resistance, better adhesion on surfaces and the ability to control hydrophobicity and color efficiency.

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The article presents the adhesive properties of a new binder based on epoxy resin with the addition of waste granite powder. The binder was modified with granite powder in amounts ranging from 10% to 60% in relation to the weight of the resin. Moreover, a coating was made without the addition of the granite powder in order to compare the obtained results. Previously obtained pull-off test results were also analyzed. The obtained results confirmed that the optimal material solution includes 10% or 20% of granite powder by weight. Additionally, chemical and microstructural analysis was also performed for both the reference sample and the sample modified with 20% of granite powder. The article also presents an explanation of the reasons for such an improvement of pull-off strength, which is based on careful analysis of the adhesive properties of the epoxy resin bonding agent modified with waste granite powder. Moreover, it explains how granite powder particles penetrate into the near-surface layer of the substrate, examines the porosity of the near-surface layer of the substrate using microstructural analysis, and presents the effect of adding waste granite powder to the epoxy resin bonding agent on the chemical properties of the near-surface layer of the substrate.

External thermal insulation composite systems (ETICS) have been extensively applied on building façades with the aim of implementing the thermal and aesthetical properties of the building envelope. However, the formation of stains and deposition of particulate matter is often observed in the surface of these systems. The use of multifunctional products with self-cleaning properties can reduce surface anomalies and thus enhance the durability of ETICS. This study aims at evaluating the effectiveness of three protective coatings with self-cleaning additives (i.e., TiO₂ nanoparticles), when applied on the surface of ETICS. Three different stains (rhodamine, methylene blue and silver paint aerosol) were applied on the ETICS finishing coat, evaluating the removal of these stains after exposure to natural (solar radiation) light source. The surface properties (compactness, hardness, roughness, gloss, and color) of the ETICS were evaluated prior and after sun exposure. Results showed that the application of the three products lead to a modification of the surface properties (compactness, hardness, gloss, roughness) of the ETICS specimens, and sensibly enhance the self-cleaning, hydrophobic and aesthetical properties of the ETICS.

The growing concerns and impending regulations on the usage of monomeric isocyanates in the production of polyurethane resins have led to the introduction of alternative non-isocyanate polyurethane (NIPU) systems. Although two-component NIPU coatings based on the reaction of cyclic carbonates and aliphatic amines have emerged as a promising option, they are still associated with two significant drawbacks: lower crosslinking densities due to reduced functionality of the oligomers and low ambient-temperature reactivity. This study reports the utilization of a hybrid approach to address these drawbacks. Amine-functional NIPU oligomers (NI-PUPA) were synthesized by the reaction of cycloaliphatic amine functional compounds and multi-functional cyclic carbonates in an excess amine molar ratio. After mixing the NI-PUPAs with (3-glycidyloxypropyl) trimethoxysilane (GPTMS), a dual-curable coating could be achieved by ambient curing of amines and epoxies and moisture curing of alkoxy silanes. A comparative experimental design was implemented to evaluate the effect of an additional curing mechanism. The results revealed that the additional moisture curing led to faster ambient curing, faster development of properties, enhanced flexibility even at higher crosslinking densities, and better corrosion resistance. Such advancement could facilitate the future implementation of NIPUs in high-performance ambient-curing coating applications.

To improve the UV resistance of cotton fabrics, three different carbon dots doped with boron and nitrogen (BN-CDs) were prepared by a one-step hydrothermal synthesis method using citric acid, ammonium citrate and glucose as different carbon sources, and ethylenediamine and borax as nitrogen and boron sources, respectively. Three types of blended aqueous solutions (BN-CDs/WPU) with BN-CDs and water-based polyurethane were sprayed on the surface of cotton fabric, and then the cotton fabric was rolled and dried. The structure and optical properties of BN-CDs were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible spectrophotometry, and fluorescence spectrophotometry. The structure and ultraviolet screening capability of cotton fabrics after finishing with BN-CD/WPU blend solution were characterized. Results showed that the prepared BN-CDs were graphite-like nanocrystals with an approximately 0.3-nm crystal plane spacing. All BN-CDs had rich hydroxyl groups and amine groups on the surface, which made the BN-CDs soluble in water. BN-CDs had a strong absorption peak in the ultraviolet region and emitted bright blue fluorescence independent of excitation wavelengths. Cotton fabrics finished with BN-CDs/WPU all showed a high ultraviolet protection factor (UPF), an excellent level of protection, and good washing durability. In particular, in cotton fabrics treated with BN-CDs prepared using citric acid as a carbon source, the UPF value was still as high as 50.1 even after washing 10 times, and the fabrics maintained good elasticity and morphological characteristics. Results thus showed that BN-CDs can be used as UV absorption agents for finishing cotton fabrics.

The depletion of fossil fuels, high environmental pollution due to the release of toxic organic compounds, and high cost are some of the challenges regarding the reliance on petroleum-based resins. Natural polyhydroxy resins (from cashew nutshell liquid, castor oil, tannins, among others) are readily available, eco-friendly, low cost, and biodegradable, and offer enhanced properties when deployed on surface coatings. Accordingly, more attention has been paid to utilizing natural polyhydroxy compounds and bio-based polyurethane resins to replace synthetic resins in the last few decades. This review presents state-of-the-art natural polyhydroxy resins and their application as precursors in surface coatings. Bio-based resins from cashew nutshell liquid (cardanol), castor oil, and tannins employed as precursors in bio-based polyurethane coatings exhibit enhanced/excellent impact strength, adhesion, flexibility, water, and chemical resistance, to mention a few. Moreover, natural resins and eco-friendly polyurethane coatings, including their methods of modification, are also reviewed. This review article helps to promote natural polyhydroxy resins as sustainable and promising green materials for the coatings industry.

The poor barrier of cellulosic paper against water vapor and oil limits its wide application as a packaging material. Lamination, extrusion, and dispersion coating are applied on paper surface to improve barrier properties. Dispersion coating can be applied to paper surface on line during paper preparation using rod coater. In the present study, an attempt has been made to increase the process speed of coating preparation by single-step process at varying pigment concentration. Coating dispersion was applied on kraft paper using laboratory rod coated and dried in hot air oven at 80°C for 5 min. Furthermore, thermal stability, water vapor barrier properties, and grease resistance of PVOH/kaolin and PVOH/talc-coated paper were studied. Additionally, the effect of single layer and bilayer coating on paper properties was also studied. Permeability model was used to predict the orientation of pigments to the surface of paper. Viscosity of both kaolin and talc-based dispersion increased with the increase in pigment concentration. Thermal studies showed that at 600°C residual mass (%) of PVOH film increased from 0.6 to 9.89% and 15% with the addition of 25% (by weight) kaolin and talc pigment. At high pigment concentration (40–50%, by weight), the highest reduction in WVTR was observed for both the pigments. Excellent coverage of paper surface and high grease resistance was observed for all coating formulations. Our study showed that talc provides better thermal and barrier properties to coated paper than kaolin.

In this work, highly fluorinated acrylate emulsions with reliable stability emulsified by protonated octadecylamine were successfully synthesized. With appropriate protonation, the obtained emulsion showed high monomer conversions up to 90.2% and ultralow surface energy. The ultralow-surface-energy coatings were fabricated via surface enrichment of abundant fluorine and replacing hydrophilic amino groups with hydrophobic groups through the Michael addition reaction. Superhydrophobic and self-cleaning surfaces were prepared on porous substrates through dip coating. When fabricated on porous glass fiber nonwoven mats, surfaces coated with enriching fluorinated side chains and few hydrophilic groups showed remarkable superhydrophobicity with a water contact angle more than 150º and a low sliding contact angle of 4.7°. The usage of fluorinated emulsions was sharply reduced due to the addition of perfluorinated acrylate. Moreover, the Michael acceptors were alternative such as perfluorinaed acrylates, long aliphatic acrylates and crosslinking acrylates, displaying superior hydrophobicity and waterproof properties. All the results conclusively indicated that this practical modified method was promising for potential applications of hydrophobic modifications.

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This study focuses on the possibility of using siloxane resins with epoxy modification to delay corrosion of metal substrates for hydraulic applications. Formulations aimed at metal protection were designed, without including anticorrosive additives, and deposited on 11SMnPb37 steel. Thin monolayer films were obtained by dip coating in different process conditions, avoiding primers. The developed procedure was simple and able to provide solid and well-anchored coatings. They were characterized in terms of morphology, scratch and wear endurance, and?resistance to a corrosive environment. The optimum formulation and deposition parameters were found. The selected coating showed remarkable adhesion to the substrate, good mechanical properties, and resistance in a saline environment, proving to be suitable as a protective barrier against corrosion. The protective effect was ensured not by additives but through the excellent adhesion of the coating and?its endurance to scratch and wear.